Bibliography style elsarticle-num-names with DOI and hyperlinks but no explicit url

Question

I prepared my article with elsarticle, using \citep & \citet throughout. I originally used apalike bibliographystyle but now need to change it to elsarticle-num-names for citation formatting requirements (see point #2 below).

Now, I am attempting to make 2 changes:

1. add DOIs to the bibliography
2. change reference style to [1] for \citep and Author et al. [1] for \citet.

I want to keep hyperref and do not want explicit URLs (only DOIs) but cannot make this work!

Thank you for any help you might have!

MWE:

\documentclass[preprint,12pt]{elsarticle}
%\usepackage{hyperref}

\journal{Test Journal}
\begin{document}
\begin{frontmatter}
\title{The Title}
\author{Prof. Big Ol' Wanker}
\address{123 Happy Lane}
\begin{abstract}
TEXT
\end{abstract}
\begin{keyword}
keyword 1 \sep keyword 2 \sep keyword 3
\end{keyword}
\end{frontmatter}

\section{SECTION1TEST}
\noindent cite: \cite{Richards1931} \\
citep: \citep{Richards1931} \\
citet: \citet{Richards1931} \\

\bibliography{library}
\bibliographystyle{elsarticle-num-names}

\end{document}

Here is the reference for Richards1931 from my library.bib file:

@article{Richards1931,
author = {Richards, LA},
doi = {10.1063/1.1745010},
file = {:D$\backslash$:/Papers/Richards - 1931 - Capillary Conduction of Liquids Through Porous Mediums - Journal of Applied Physics.pdf:pdf},
issn = {01486349},
journal = {Journal of Applied Physics},
pages = {318},
title = {{Capillary Conduction of Liquids Through Porous Mediums}},
url = {http://scitation.aip.org/content/aip/journal/jap/1/5/10.1063/1.1745010},
volume = {1},
year = {1931}
}

without hyperref (wanted hyperlinks present, DOI displays correctly, but unwanted URL is present):

with hyperref (hyperlinks not present, DOI displays incorrectly, and unwanted URL is present):

Answer 1

This problem occurs because elsarticle does not define a \doi macro that hyperref requires.

Hyperref calls \doi{\bibinfo{doi}{XXX}} to produce the URL for the DOI in the reference XXX. If the \doi macro is not defined, the resulting output will be something like \let\@tempa\bibinfo@X@doi{XXX}

As a workaround, you can define a \doi macro that solve the problem

\documentclass{elsarticle}

\usepackage{hyperref}

\makeatletter
\providecommand{\doi}[1]{%
  \begingroup
    \let\bibinfo\@secondoftwo
    \urlstyle{rm}%
    \href{http://dx.doi.org/#1}{%
      doi:\discretionary{}{}{}%
      \nolinkurl{#1}%
    }%
  \endgroup
}
\makeatother